DE3006098C2 - - Google Patents

Description

The present invention relates to a method for manufacturing position of shaped bodies made of ceramic or metal with the Preamble of claim 1.

According to a method described in DE-OS 27 15 563 is a ceramic powder in the manufacture of the moldings or a metal powder mixed with a resin, the Mi shaped to obtain a green body and min least a part of the binder by treating the Green body with a solvent for the binder away. The green body heats up to a temperature heated above the melting point of the binder and he warmed green bodies in a vapor of the solvent brings. Then the green body is placed in a bath immersed liquid solvent for the binder, and finally the product treated in this way is Ent Removal of the remaining binder burned.

The known method is usable Binder and solvent limited. Furthermore is the procedure for removing the binder from the green body complex and complicated. On the other hand, it is known to produce molded ceramic parts a mixture of binder resin and Ceramic powder by means of an injection molding or injection press  deform the process and then that in the ge molded product to decompose or encapsulated resin burn out. In such a case, only by a heat treatment of the molded body removal However, despite precautions such as for example an extremely slow temperature rise tion, the formation of cracks or an expansion or de formation of the molded body can not be prevented. The known processes are therefore not satisfied industrially presenting.

It is therefore an object of the present invention to industrially advantageous process for the production of To create shaped bodies made of ceramic or metal, in which the binder resin from the green body to efficient Way removed and a fired molded body without defor mations or cracking is obtained.

This object is achieved by the main one Proceed marked procedure solved.

Preferred embodiments of the invention are in the sub claims marked.

A plasticizer is preferably added to the mixture remains the soluble in the organic solvent Resolve resin content effectively and at the same time the Improve ductility and increase density.  

The mixture of a ceramic powder or a metal powder and the two types of resin mentioned, namely that in the organic solvent-soluble resin and the un soluble resin, are preferably a plasticizer and incorporates a lubricant.

The orga used in the method according to the invention nical solvents should be used as components Certain ceramic materials used inert and should not resolve them and should preferably easily accessible, relatively economical and simple, d. H. be handled without risk of explosion.

The division of the solution in an organic solvent or in an organic solvent insoluble resins depends on the conditions. The in the following combinations can be used as optimal case games are viewed. The combinations of those soluble in the organic solvent or insoluble resins with the appropriate solvents can be chosen freely.

The following are typical Kombina options called. The are used according to the invention set solvents classified as follows.

• (1) Aromatic hydrocarbons:
  Benzene, toluene and xylene;
• (2) substituted aromatic hydrocarbons:
  Nitrobenzene, phenol, m-cresol, chlorobenzene, bromobenzene and o-dichlorobenzene;
• (3) halogenated hydrocarbons:
  Chloroform, methylene chloride, dichloroethane and dÿodoethane;
• (4) Ketones:
  Acetone, methyl ethyl ketone and methyl isobutyl ketone;
• (5) esters:
  Ethyl acetate and butyl acetate;
• (6) cyclic ether:
  Tetrahydrofuran and dioxane;
• (7) aprotic, dipolar solvents:
  N, N-dimethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide;
• (8) Alcohols:
  Methanol, ethanol, propanol and butanol; and
• (9) aliphatic hydrocarbons:
  Propane, butane, hexane, octane, decane, propene, butene, hexene, octene and decene.

The solubility of the respective resin in the respective solution by a simple test be true. The solubilities of Resins specified in the solvents.

Resins of the type insoluble in organic solvents

Polyalkenes:
Polyethylene, polypropylene, poly-4-methyl-1-pentene and polybutene; insoluble in solvents (1) to (9);
Polyvinyl alcohols:
insoluble in the solvents (1) to (9);
Polyacetals.
insoluble in solvents (1), (4), (5), (8) or (9);
Polyvinyl butyrals:
(Acetal degree greater than 70%) insoluble in solvents (1), (5) or (9);
Polyvinyl butyrals:
(Acetal degree less than 70%) insoluble in solvents (1), (2), (3), (4), (5), (6), (8) or (9);
Polycarbonates:
Poly- (oxycarbonyl-1,3-phenylene, poly- (oxycarbonyl-1,4-phenylene) - insoluble in solvents (1) to (9); poly- (oxyethyleneoxyter phthaloyl) - insoluble in solvents (3) to (5) and (8) and (9);
thermoplastic polyurethanes:
insoluble in solvents (1) to (6), (8) and (9);
Polyamides:
(a) 4-nylon - insoluble in solvents (1), (3), (4), (5), (6) and (7); (b) 6-nylon - insoluble in solvents (1), (3), (4), (5), (8) and (9); (c) 6,6-nylon - insoluble in solvents (1), (3), (4), (5) and (9); (d) 6,10-nylon - insoluble in solvents (1) and (3) through (9); (e) 11-nylon - insoluble in solvents (1) through (6), (8) and (9);
Polyvinylidene chloride:
insoluble in the solvents (1), (2), (8) and (9);

Resins of the type soluble in organic solvents

Polystyrene; ABS and AS:
(Acrylonitrile butadiene styrene; acrylonitrile styrene) - soluble in the solvents (1) to (7) and (9);
Polyvinyl chloride and copolymers:
soluble in solvents (1) to (7);
Polyacrylate and copolymers:
soluble in the solvents (1) to (7);
Polymethacrylate and copolymers:
soluble in solvents (1) to (8);
Polyvinyl acetate and polyethylene vinyl acetate:
soluble in solvents (1) to (8);
Acetyl cellulose:
soluble in solvents (2) to (5), (7) and (8);
Polyester:
Polyethylene terephthalate and poly butylene terephthalate - soluble in solvents (1) to (7);
Polycarbonates:
Poly- (oxycarbonyloxy-1,4-phenylene isopropylidene-1,4-phenylene) - soluble in solvents (2), (3), (6) and (7); Poly (oxycarbonyloxy-1,4-phenylene-2-pentylidene-1,4-phenylene) - soluble in the solvents (1) to (3) and (5) to (7);
Polyphenylene oxides:
soluble in solvents (1) to (3).

The solubility of the resin in the respective solution depends on the molecular weights of the resins as well on temperature and other factors. You can do that respective solubilities, however, by simple tests easily determine.

When choosing the combination of the in an organic Solvent-soluble resin and in an organic The solvent-insoluble resin is preferred a matrix of the soluble in the organic solvent Resin formed.

Preferably, a plasticizer for the in the organi mixed solvent-soluble resin. Thereby the molding process can be carried out easily and the resin can be easily removed from the molded body the. The density of the product obtained by burning out is increased without cracking. Under Be access to the description in Encyclopedia of Polymer Science and Technology, Volume 10, pages 228 to 306, suitable plasticizers can be selected.

Typical plasticizers include phosphoric acid esters such as Tricresyl phosphate, triphenyl phosphate and cresyl diphenyl phosphate; Phthalic acid esters, such as butyl octyl phthalate, Di butyl phthalate, dicyclohexyl phthalate, diethyl phthalate, di hexyl phthalate, diisodecyl phthalate, di-2-methoxyethyl phthalate, dimethyl phthalate, ditridecyl phthalate, di-2- ethylhexyl phthalate, diisooctyl and mixed octyl phthalate, n-octyl-n-decylphthalate, isooctylisodecyl phthalate and other phthalic acid esters; Trimellitic acid ester; other aromatic plasticizers; Adipic acid esters, such as diisodecyl adipate, di-2-ethylhexyl adipate, octyldecyl adipate, diisobutyl adipate, diisooctyl adipate and others  Adipates; Azelaic acid esters; complex linear polyester and polymeric plasticizers; epoxidized esters, such as epoxidized soybean oil and octylepoxy tallate; Dibutyl maleate; Glycerin monoricin oleate; Isopropyl myristate; Isopropyl palmitate; Oleic acid esters, such as butyl oleate, glycerol trioleate, methyl oleate, n-propyl oleate and isopropyl oleate; Phosphoric acid ester; Sebacic acid esters such as dibutyl sebacate and di- (2- ethylhexyl) sebacate; Stearic acid esters such as n-butyl stearate; other stearic acid esters and stearic acid; as well as tri ethylene glycol di (caprylate caprate). Especially with the Resins of a type soluble in organic solvents can, depending on the respective resins, further soft be used.

The ratio of that dissolved in the organic solvent resin to that in the organic solvent soluble resin is preferably in a range of 95 to 30% by weight: 5 to 70% by weight. If the amount of the first ren less than 30 wt .-% and the amount of the latter more than 70% by weight, the disadvantages of the are observed conventional procedure. If, on the other hand, the share of the first mentioned resin more than 95 wt .-% and the proportion of the latter type of resin is less than 5% by weight, can in the form produced by injection molding deformation during handling or causing the breakage.

It is particularly preferred 85 to 40 wt .-% of the solution Lich resin and 15 to 60 wt .-% of the insoluble resin to combine. With these conditions, no defor Mation or breakage of the shape obtained by injection molding body observed. The procedure for removing the resins is simple and there is no cracking or expansion on.  

As a resin soluble in organic solvent be preferably polystyrene, polyvinyl chloride or polyoxy-1,4- phenylene sulfonyl-1,4-phenylene used. As in organi Resin-insoluble resin is preferred Polyethylene, polypropylene (isotactic) or a poly vinyl alcohol used. These resins are therefore before increases because the deformability caused by injection molding is good and does not crack or expand is caused. The resins mentioned are invented by the process according to the invention is therefore particularly preferred puts. When dissolving the resin in the organic solvent solvents can be two or more types of solvents be used and it is possible for the resins to subsequently dissolve in each of the solvents.

According to the invention, the resin can be combined with a Plasticizer and a release agent and a filler be used if this does not cause any difficulties caused. It is particularly preferred to use one Incorporate plasticizers. The weight ratio of the Plasticizer to the resin depends on the conditions the injection molding process, the types and Amounts of resins and the ratio of ceramic powder or metal powder to the resin and lies preferably in a range from 1 to 50% by weight: 99 to 50% by weight and in particular in a range from 3 to 30% by weight: 97 to 70% by weight.

Suitable ceramic materials, which according to the invention include silicon nitride, alumina, Zirconium oxide, silicon carbide, cordierite, tungsten carbide, Aluminum nitride, aluminum titanate, zircon and mullite.

The method according to the invention can also be applied to a spray press molding process are used in which a metal  powder is used instead of the ceramic powder. Ge Suitable metal powders include silicon, titanium and zircon.

The molding process is not critical. Preferably an injection molding or an extrusion molding process or a similar process to the specified strived to achieve results.

The volumetric ratio of the ceramic powder or Metal powder to the entire mixture is made accordingly selected to obtain a moldable mixture, and is preferably in the range from 25 to 75% by volume, ins special 38 to 55% by volume. If the ratio is lower than 25 vol%, the amount of resin is too small to be a To carry out molding processes. If, on the other hand, the ratio is greater than 75 vol%, the shrinkage in the Burn-out reaction level too large and it is difficult rig to remove the soluble resin and the dimensional accurate To ensure speed of the molded body.

The machine used to carry out the transfer molding process or the extrusion molding process and the Molding processes are not critical. It can be a conventional machine and a conventional process will.

The molded product is treated as follows. The Shaped body is in a bath of an organic solvent dipped to remove the soluble resin from the molded body dissolve and transfer into the solvent. Man can stir the organic solvent or a Apply ultrasound treatment or dissolve using speed up other procedures, provided that the Shaped body is not deformed or broken.  

In the process according to the invention, the rest Resin removed by a burnout process. When ver burned out stage of the molded body Lich heated to about 350 to 450 ° C. Zim temperature up to about 250 ° C the temperature around 50 ° C / h increased. From about 250 to about 450 ° C, the tem temperature increased by about 100 ° C / h, and usually the Molded body heated at about 450 ° C for about 1 h. The temperature and the conditions under which the burnout takes place can depend on the type of resin, in particular depending on the type of insoluble resin, who varies the.

The device used for burnout can be an electri be of the type in which hot air is circulated to be led. It is also possible to use the molded body in the process stage of burning out to a tempera to heat in which not only the remaining resins removed, but also the calcination and that Sinter the ceramic powder or the metal powder to step. The effect of the plasticizer is also in the Burnout process stage observed.

There were the times when the dissolution of the Resins are needed. The release time is as follows dimensions determined: It is by deformation of the respective Resin by means of an injection molding process (Pellets) with a cross-sectional area of 4 × 4 mm (2.5 g) formed that have no porosity. 2.5 g of from the Resin-formed pellets are in 50 g of the respective Lö solvent stirred vigorously at 20 to 50 ° C, and it will determines the time it takes to dissolve all the resin. The soluble resins used according to the invention should a dissolving time of less than 100 h and preferably we  have less than 50 h. The used according to the invention insoluble resins should have a dissolving time of more than 100 h.

In the following the invention is illustrated by examples and Comparative examples explained in more detail.

Example 1

In a kneader designed as an autoclave, put 76.4% by weight (50% by volume) silicon nitride powder, 15.3% by weight Polystyrene, 3.8% by weight of polyethylene, 2.8% by weight of stearic acid and 1.7 wt% diethyl phthalate. The components are un kneaded at a pressure of 2.5 bar at 180 ° C The mixture is pellets with diameters from 3 to 5 mm shaped. A pelletizing mold is made with the pellets procedure carried out. This is done with an injection press at a cylinder temperature of 250 ° C below one Injection pressure of 981 bar and a mold temperature of 50 ° C a plate with a size of 60 mm × 100 mm × 8 mm receive. The resulting plate is in for 40 h at 15 ° C Methylene chloride immersed in a 2 liter tank with lid. By determining weight loss of the product is found to be about 93% by weight of the total of polystyrene, stearic acid and diethyl phthalate have dissolved. There is no cracking in the product and no deformation was observed. The product is in Nitrogen atmosphere burned out by going at a rate heated from 200 ° C / h from room temperature to 1750 ° C. There the remaining resins and the product are removed is sintered. The sintered product has no cracks or Deformation on. The dissolving time at 30 ° C of polystyrene in methylene chloride is 0.15 h. On the other hand, the Dissolution time of the polyethylene in methylene chloride at 50 ° C more than 100 h.  

Example 2

The procedure of Example 1 is repeated. Under Ver using 77.3% by weight (52% by volume) of silicon nitride powder, 13.8% by weight of polyvinyl chloride, 5.9% by weight of polypropylene (iso tactical), 1.5% by weight of diethyl phthalate and 1.5% by weight of stearin acid pellets are made and it is made with the A pelletized injection molding process was carried out to produce a Obtain mold plate. The resulting molding plate will 41 h at 15 ° C immersed in tetrahydrofuran, which in the used in Example 1 tank was filled. By Be one finds mood of the weight loss of the product, that about 92% by weight of the total amount of polyvinyl chloride, Stearic acid and diethyl phthalate have dissolved. It there is no cracking and no deformation of the product observed.

Following the procedure of Example 1 is a sintered product produced. The sintered product shows no cracks and no kei no deformation. The dissolution time at 20 ° C of polyvinyl chloride in tetra hydrofuran is 0.67 h. On the other hand, the dissolution time of isotactic polypropylene in tetrahydro furan at 50 ° C for more than 100 h.

Examples 3 to 7 and Comparative Examples 1 to 4

The procedure of Example 1 is repeated in each case. There however, the resins and the ceramic powder or the metal powders as well as the plasticizers and other additi ve used, which are listed in the following table. Varying the reaction conditions Sintered products manufactured. The results are in the Table summarized.  

table

Table (continued)

Claims (9)

1. A process for the production of ceramic or metal moldings by mixing a ceramic powder or a metal powder with a resin, molding the mixture, removing at least a part of the binder by treating the molded product with a solvent for the binder and then firing the so be acted product with removal of the remaining binder by, characterized in that a mixture of resin soluble in organic solvent and resin insoluble in the same organic solvent is used as a binder and the molded product before firing to dissolve the organic solvent-soluble resin in a liquid immersed organic solvent. 2. The method according to claim 1, characterized in that that to dissolve the in organic solvent Lichen resin the organic solvent from the group selects from aromatic hydrocarbons, sub substituted aromatic hydrocarbons, halogenated hydrocarbons, ketones, esters, cycloethers, aprotic dipolar solvents, alcohols and ali phatic hydrocarbons. 3. The method according to claim 1, characterized in that you add a plasticizer to the mixture. 4. The method according to claim 3, characterized in that the plasticizer with at least that in organic Lö solvent-soluble resin is mixed. 5. The method according to any one of claims 1 to 3, characterized characterized in that the ceramic powder and / or metal powder in a volume ratio, based on the total amount of the mixture, used in a range of 25 to 75 vol% is. 6. The method according to any one of claims 1 to 5, characterized characterized in that one has a weight ratio of in orga Resin soluble in organic solvent solvent-insoluble resin chooses that in a range from 95 to 30% by weight: 5 to 70% by weight. 7. The method according to any one of claims 1 to 6, characterized characterized in that the ceramic powder is silicon nitride, Aluminum oxide, zirconium oxide, silicon carbide, cordierite, Tungsten carbide, aluminum nitride, aluminum titanate, zircon and uses mullite.   8. The method according to any one of claims 1 or 3, because characterized in that the metal powder is silicon, Titanium or zirconium is used. 9. The method according to any one of claims 1 or 3, because characterized in that as in organic solution medium soluble resin uses a resin that is 20 to 50 ° C in less than 100 hours in one amount of 5 wt .-%, based on the solvent.